In the Transform dialog (Shift+Ctrl+M) you can Move, Scale, etc. ...
For example, you can scale by different units: mm, pc, pt, in, cm, px and %
For some cases it would be nice if you could move several selected objects by % relative to their size, especially when you select "Apply to each object individually". However, apparently you can't.
Is there maybe a workaround?
Would it be worth a feature request?

Some ideas can be evaluated according to how often people who use the program regularly actually need to do this task, and the answer for me is - never, in all these years. Not saying that some day it might not be momentarily useful....
Without knowing your exact project I can't offer you a solution but what comes to mind right away is scaling up from one corner and then scaling down from the opposite corner. Obviously not practical for many objects though

There are probably some times when I would have found that useful. Guides can already be moved relative to each other, although I'm not sure if percent is an option.

I don't know how hard or easy it would be to add such a feature, but I can see how it could be useful for some users in some situations. In fact, as a shortcut to doing simple math, I might come to depend on it more and more. Although it's always hard to put a specific value on "what if?"

I wonder if it might have already been requested?

Edit
Hah! Actually now that I think about it, a relative move in percent wouldn't work for guides, because they have no volume. It would have to be relative to page size or relative to another guide maybe?

Oh! I didn't realize that you could already move things relatively with Transform dialog. There's just no end to what you can learn about Inkscape!

So relative to object size? Would you find relative to page size helpful?

@druban, I completely agree that developers cannot jump on every single "nice to have feature" which a single person mentions. By the way, is there any way where users can vote for suggested features which will be then maybe realized? Maybe Launchpad? But how many Inkscape users, or Forum members also have an account on Launchpad?

To your suggestion: scaling up from one side and scaling down from the other side. Sounds ok (theoretically). But I don't know how to do this since Inkscape only scales from the bottom left corner or the center of the object.
This brings me to another missing point in Inkscape: set the Base point for position (shift) and size (scale).
LibreOffice offers this which I find pretty useful (see image below).

Ironically, with tiled clones in Inkscape it is the opposite: you can only shift in % of object size but not in absolute units like mm, cm, etc. for example to create a regular pattern where the distance of repetition is independent of the object size.

Yes, on launchpad, there is an 'Affects me, too' button, that increases the 'heat' of the bug report.

Yes workaround for tiled clones as with patterns etc is to use an invisible or later to be deleted object to set the desired distance since this object will transform too it's actually the better way to manage this