Hey Andre,
Currently I am not really sure what is the whole purpose of this Joomla #__finder_tokens table, but it related with the Joomla smart search functionality.
And this table is not only store 1 extension data, you can check this from your site backend > plugins > filter type to finder (screenshot :
https://take.ms/xhK7G) so you can see which finder plugin is enable now, mean user can able to search all these data through Joomla smart search in frontend.
I found one of the thread similar with this issue from Joomla forum
https://forum.joomla.org/viewtopic.php?t=954273 , perhaps you can try increase these following directives from your mysql my.cnf file and see how it goes?
- max-heap-table-size 64MB
- tmp-table-size 64MB
You can consult with your webhosting provider regarding this and see where is your mysql my.cnf file location.