Although it's possible to use GIMP to create work like this manually by copying and pasting, it's not the best kind of software to use for this.
Use Inskcape instead. It's a vector image editor, and it's free and open source like GIMP. It has a feature called "clones" which could solve your problem. This is very similar to what is sometimes called "symbols" ...
No magic bullet AFAIK, but no need to copy/paste.
Worst case, if the square positions are random:
Make a first square as you wish
Select and copy this square to the clipboard
Start the paint brush oe pencil and set it to clipboard (this is always the first in the list)
Paint all remaining squares with a single click on each. If necessary lock the alpha to ...
I'm sorry that you're finding the pattern tool frustrating to use. Hopefully, this answer might help clarify a few things. First, we'll tackle using the pattern options panel and then I might be able to help you optimize your pattern to reduce its complexity.
I noticed in your photo that you don't seem to have a pattern options panel. When you start a new ...
Use the copy/paste/create pattern method for Photoshop.
And since it's simple one-color artwork, paste the artwork as a Shape Layer.
Do this larger than normal, in a high resolution document. In other words, paste your hand into a large 300PPi Photoshop document as a Shape Layer and then define the pattern.
By doing this you create a high resolution ...
TL;DR: No, but there are some hacks.
I'm not sure how useful they will be for your particular use case, but here goes:
As far as I know, there is no way to make the stroke-dasharray change dynamically as you adjust the length of the line, at least not by moving an end node.
However, you can edit the stroke-dasharay in the XML editor manually.
For your needs the scatter brush suggestion may work. Be aware though that scatter brushes place each instance independently, You won't get the "skewing" and "distortion" on curves the same way a pattern brush distorts. So, it really depends upon the desired artwork.
Adjust the defining rectangle for the pattern.
Drag the Pattern Brush artwork to the ...