Hey there!
I just wanted to know if is there a way to edit multiple frames at the same time. I need to resize a part of an animation so it would be very useful
Thanks a lot in advance!

After selecting multiple frames, with Ctrl-click and Shift-click, all you can then do is copy/cut/paste them and click-drag them. You can't do an edit operation like resize or move on all of them, only on the one that the frame marker is on.

If you render a range of frames out to a .png image sequence, you can import them all at the same time into the image as separate layers. They can then be grouped and the group can have resize, move, etc done to it. You'd then have the task of converting each individual layer of that group to an animated layer/frame by right-click Create Duplicate Frame in the Timeline and then copy/pasting the frame to the required destination in your main animation layer(s).

I don't know of any way to export a group of layers as a set of .png images (except for manually doing it for each layer). If you could do that then you could use Import Animation Frames to bring them all in as an animated frame sequence, instead of the manual conversion method described above.

As an additional complication, there's a bug https://bugs.kde.org/show_bug.cgi?id=409044 which may result in you being unable to render a .png image sequence with transparency. Krita version 4.1.7 isn't affected though.