Thanks
One part solved; it would still be nice to have it as a functionality.
For those that need a query to extract tags with tag groups in the format that is also used for the upload of tags / tag groups, the below query will do that
SELECT t.name as tag, tg.name as "tag group"
from tag_groups as tg
left join tag_group_memberships as tgm on tg.id = tgm.tag_group_id
left join tags as t on tgm.tag_id = t.id
where tg.name = 'boards-and-microcontrollers'
order by tg.name asc, t.name asc
Next you can save to csv (or json) after running the query.