A couple of suggestions

I use serial monitor a lot and copy data into spreadsheets.
It would be useful if there was a highlight and copy facility.
I know it's at odds with what the serial monitor is there for, but if CTRL-C works, why not have a drop-down?
It's just with my setup, the keyboard and mouse are inconveniently apart (short of desk space), so a lot of getting up and down. I suppose it's exercise.
The other thing I would like to be able to do is highlight text in sketches in different colours to make it a little easier when editing large sketches. I'm not talking about selecting and copying etc., but a temporary or permanent highlight.
At the moment, I resort to copy the sketch into a spreadsheet and do it there.

Thanks for your input tigger!

tigger:
It would be useful if there was a highlight and copy facility.

There's an existing pull request to add this feature:

There are test builds downloadable from that link if you want to try it out.

From the discussion there, it sounds like the Arduino developer facchinm is receptive for adding this functionality, but perhaps via a different UI (context menu).

tigger:
The other thing I would like to be able to do is highlight text in sketches in different colours to make it a little easier when editing large sketches. I'm not talking about selecting and copying etc., but a temporary or permanent highlight.
At the moment, I resort to copy the sketch into a spreadsheet and do it there.

I'm not too sure about this one. The IDE is intended to be very beginner friendly and each UI element added makes it more intimidating to the beginners. It's not to say that we should never add new UI elements, it's just that we need to carefully weigh their benefit against the added complexity. I'm sure the highlighting feature would be useful to some, but probably most people would never use it. The IDE has a nice feature File > Preferences > Use External Editor that lets you use any text editor you like to write your code, then just use the Arduino IDE only for compiling, uploading, installing libraries and boards, etc. There are many great free text editors that have lots of advanced features. So if you can find one that has a highlighting feature, that might be a good option, certainly better than using a spreadsheet application. I like Notepad++ (Windows only) and it does have a feature where you can highlight text, right click, and then select any of five different configurable styles from the "Style Token" submenu. I'm sure other editors have similar features.

That said, we now have the Arduino Pro IDE in the works, which is targeted to advanced users. So it's not so much of a concern about keeping the number of UI elements to a minimum with that IDE. I'm not very familiar with the new IDE, but I don't see that it has an existing highlighting functionality. The Arduino Pro IDE is currently in its early stage and Arduino is seeking input and testing from the community. So if you like, you can give it a try and submit feature requests:

facchinm is Martino Facchin

... and Juraj is Juraj Andrássy. Now I've told you something you knew for years too!

pert:
... and Juraj is Juraj Andrássy. Now I've told you something you knew for years too!

on GitHub I have a login jandrassy and I don't like if someone uses it as if it was a name or nick. One blog even mentioned me as the author of some library but used Jan Drassy. When I created the login on GitHub, I didn't know that it will be used as nick name all over GitHub and now I can't change it. So I imagine others are in the similar situation and I try to use the name, not the login when I am referring some github user.

Well, Jan (haha), at least you aren't stuck with a stupid user name like "per1234" or "pert"! At the time I signed up, I didn't think I'd do much with my GitHub or Arduino Forum accounts so I just tried "per" first, which of course was taken, and then grabbed whatever came up available after that. Whoops!

I intentionally used "facchinm" here because that's the name tigger would see if they went to that link. But I see your point. People like you and Martino Facchin should get the full recognition for the amazing work you do.

Hello pert
Thanks for all the useful information which I will digest
I don't construct sketches in a spreadsheet, but I do use them to get a better view of things, by separating comments and so on to see the real meat.
Being able to use colour helps with nested "ifs" and so on and tabbing in columns helps with the structure.
I do use and like Notepad+++. It's comprehensive with lots of powerful features and all credit to the author(s).
Sometimes I curse the IDE, but I never forget how much work goes into it.
I don't remember how I got into Arduino, but it must have been chance. I love turning text into flashing lights. Learning hardware and software has been a challenge. I stand in awe at the power on a sliver of silicon.
Now I look around the house and think where a 328 might come in useful - unfortunately, it leads to an untidy mess of half-finished projects
As for daft nicknames, I like the inhabitants of Hundred Acre Wood which is not too far from me.
Cheers