Version 3.67.03 adds a small command line utility SbieIni.exe which can be used to query and update the Sandboxie.ini configuration file from the command line. It should be fairly straightforward to use and it includes built-in help when started without any parameters. One possible use is in the creation of more complicated scripts to adjust Sandboxie configuration in various ways.

Nice addition!

I thought you might like it

Well damn.. and that 2 days after I wrote a go lang package for it myself

When you say "update", is it like Reload Configuration, which does not take effect on sandboxed programs that are already running?

Yes.

[ZZ]
Enabled=y
ConfigLevel=7
RecoverFolder=%Personal%
RecoverFolder=%Favorites%
RecoverFolder=%Desktop%

I know that I can add "C:\Downloads" as a Recover Folder using either of these:
sbieini insert ZZ RecoverFolder C:\Downloads
sbieini append ZZ RecoverFolder C:\Downloads

The "set" parameter needs to be used with care:
sbieini set ZZ RecoverFolder C:\Downloads

I assume that this is the expected result:
[ZZ]
Enabled=y
ConfigLevel=7
RecoverFolder=C:\Downloads

SbieIni set <section> <setting> <value>
- replaces a setting with a new value. If value is omitted, the setting will be removed entirely.

Yes, set is designed to completely replace a value. The mechanism does not make a difference between single-line and multi-line settings. "set" is intended for use in single-list settings, "insert/delete" for multi-line settings. But there is no reason that you can't use "set" to overwrite multi-line settings.