I just found out that Z7F doesn't do anything audible in Impulse Tracker, but it resets the filter on the next note. OpenMPT, Schism Tracker and probably other software only respects the latter part, but still applies cutoff on Z7F.

First step is done: Zxx macro interpretation is complete now. Some macro letters have been changed / added in this process, see the "macro help" button in the macro settings.
Macros can now also make use of volume / panning envelopes, however this does not work very well yet "between the rows" (neither with Zxx, nor with \xx) - this is still a big TODO!
Handling of those things is expected to change in the future, so don't rely on the buggy behaviour.

TODO:

• Envelopes are not processed if an instrument has no sample assigned (unless Compatible Mode is activated); it appears that an empty sample slot is enough, though, no actual sample data is required.
• There should be per-instrument or per-VST panning / volume macros that are applied automatically.

The TODO from comment 273 has been fixed. The other TODOs are still left.

Z7F handling should also be fixed in compatible mode.

Fixed envelope processing if there is sample assigned. Per-instrument macros will get their own issue.