There are plenty of plugins for Accordion / Concertinas. But nothing in GenerateBlocks.
The JS and CSS only needs to be added to your site once.
For the content.
I would first create a single Headline followed by a single Container block, put in some dummy content, style them and add the Additional CSS classes.
Once i was happy i would select both blocks – by shift clicking the two ( Gutenberg can be a little fiddly with this ).
When both are selected you can select Add to Reusable Blocks
from the 3 dot menu in the toolbar.
Then whenever you need to add collapisble blocks simply add New Block > re-usable block.
Then From the blocks toolbar 3 dot menu now: Convert to Regular Block
so you can edit the content.
You can then duplicate the Headline and Container blocks from the same menu to create a stack of them 🙂