Liquid is an extendable language. Starting with documentation on what has been implemented on other systems is reasonable. See this post
The difficulty you will experience is mostly related to the fact
- such documentation is only a starting point. The implementation in Manager is not exactly the same.
- There is no wiki listing filter / procedure calls which are available and the parameters they support
- There is no wiki listing the variables exposed
- There is no wiki listing html functions supported
- The advance programming interface is really low level program hooks subject to change as the program evolves. So any customisation you do will require maintenance.
- There is no forum to discuss advanced customisation of Manager and discussion on this forum is discouraged. I assume because advanced customisation is beyond most accounting program users.
The usual answer is the program is “self documenting”, just reverse engineer what is already exposed.
Not surprisingly few users take the time to actually use such an environment although many can see its potential.
Searching for example code on this forum is really the only resource available.