There is no “URL scheme builder”. The URL scheme is typically meant for use in the Shortcuts application. Do also look at the Shortcuts Actions section fo the Help as well, as URL schemes aren’t the only option.
Be aware though in DTTG version 3 it is no longer possible to transfer the UUID (a unique number of each DT record) as input into Shortcuts, as this appears to have been deliberately removed to my disappointment.
The Shortcut actions appear to have been primarily designed as a ‘one-way street’ (from Shortcuts to DTTG and not the other way around) which seriously criples it’s usability IMO.
Apparently some apps didn’t use the correct input if content was shared from DTTG to that app, but removing the UUID seems somewhat of a crude counter measure to circumvent that problem if you ask me, as Shortcuts could easily be used as a filter to do that for example.