Create connection for target system in SM59 - for each possible target in transport (e.g. 'SYSTEM', 'SYSTEM.MANDANT' ) create connection with exact same name - will be used to call RFC which unpacks transport. So ZZZ.999 for system ZZZ and mandant 999, or just ZZZ if you don't specify mandant in transports.
[Optional] Set developer system as trusted (via transaction SMT1) at target system. Set Trust Relationship to yes in connections and use Current User. This way you won't have to log into target system everytime you wan't to import transport - you will be automatically logged with current user.
Notes
Written in ABAP 7.50
Changelog
v1.1 - allow user to choose between 3 types of descriptions - ToC + original request number, original request description, or custom / numbered description
v1.2 - allow user mass action on all selected ToCs
v1.2.1 - add STMS button
v1.3 - retry importing ToC for a specified amount of time if not yet visible in target system (apparently, release funciton isn't fully synchronous?)
v1.4 - add support for sub transport, minor enhancements
11.09.2025 - add support for selecting different target system (thanks for idea jrgkraus
17.09.2025 - add support for transport groups
11.02.2026 - read variant with current username on report initialization