As you mentioned Debian - you would likely be able to get hold of a Debian package and that can be unpacked and converted to a PKGBUILD either by means of debtap or manually using [root tip] [How To] Install a .deb package on Manjaro as a starting point.
Another option is to create a PKGBUILD that build from source.
Just looked at the source - install qtcreator - and compile the source.