v0.68.0 will be hitting soon, and a new feature is being added to the building sidebar on Desktop devices, a text filter:
It works about how you would expect. You start typing in the name of a building you are looking for, and the list filters as you type. The filter input box only shows up if there are so many build options that you need to scroll to see them. So for example, if you choose 'Farming' from the drop down filter and there are only a handful of farming options, then the input box doesn't show up.
Anyway, I am also looking at a way to add this to the mobile UI, but it will not be coming in this weeks update.