Not every specialised activity during a patrol needs its own sign-on. LIMSOC handles drones and IRBs differently, depending on whether your unit type is configured to run a separate linked sub-patrol for them.
Drones
Drone operation is recorded as a field on your main patrol — it doesn't create a separate patrol record. If your unit is configured for drones, you'll see a drone option as part of your patrol's sign-on or activity screen, where you record the operator and aircraft details for the session.
Some units also review drone flights afterwards through a separate Drone Flights reporting screen at the unit level — this is for reviewing past flight records, not for signing on.
IRB crew tags
If your unit doesn't run a separate IRB sub-patrol, IRB driver and crew duties are recorded as role tags against members on your main patrol's roster — the same as any other on-patrol role — rather than as their own patrol.
IRB Patrol as a linked sub-patrol
LIMSOC also supports a genuine IRB Patrol type: a separate patrol record linked to your main patrol as a child, with its own sign-on, its own roster, and its own sign-off, run alongside the parent patrol for as long as the IRB is operating. Where this is configured for your unit type, it appears as a Manage Sub-Patrols (or similarly named) option on your patrol's activity screen, letting you sign an IRB Patrol on and off independently of the main patrol.
This linked sub-patrol option isn't enabled for every unit type — whether you see it depends on your unit's configuration. If you expect to see it and don't, contact your administrator to check your unit's patrol type setup.