Merge branch 'adinapoli/issue-342' into 'dev'

Forest of trees: restore hierarchical grouping of terms

Closes #313

See merge request !424
4 jobs for dev in 98 minutes and 52 seconds (queued for 17 minutes and 17 seconds)
Status Job ID Name Coverage
  Cabal
passed #18897
cabal

00:45:10

 
  Stack
passed #18898
stack

00:06:14

 
  Bench
manual #18899
allowed to fail manual
bench
 
  Test
passed #18900
test

00:47:27