Change sidebar of "RISM Sigla Directory"

[jenniferward]

Not urgent - but could you please change the sidebar "RISM Sigla Directory" to "Directory of RISM Sigla" so that it matches the title of the directory more closely? (I assume space is an issue, so this is a shortened form here.)
https://stage.rism.info/community/sigla.html

I found the yml file but don't know how to change it.