Cell Towers can be used as a crude location based trigger in order to trigger macros when you enter or leave a certain area. Since cell towers typically have a range of several KM the accuracy is not comparable to a GPS location fix and if you require a very specific area you should look at the Geofence trigger instead.
The advantage of using cell towers as a trigger is that less battery power will be used overall. The trigger works by periodically scanning what cell towers can be seen and if determining if you are inside or outside of a cell tower group. If you have transitioned from outside to inside a group then the enter trigger will fire. If you transition from inside to outside a group the exit trigger will fire.
Note that you will need to grant MacroDroid location permission in order to detect cell tower ids and since Android 8 you must have location services enabled for cell tower detection to function.
Cell Tower Groups
A cell tower group typically consists of multiple cell towers that can be seen from a fixed location. All towers within this group are then treated as one and the same in order to determine if you are inside our outside that cell tower group area. To add a new cell tower group click the cell towers button from the home screen and then the plus button on the cell tower list. Assign a name to the cell tower group (e.g. home) and click ok. The app will then scan for cell towers that can be seen and add them to the group. It is recommend to leave the scanning to happen for an extended period in order to detect all towers around. You can select to scan in the background and the scanning will continue to add any new cell towers to the current group. You will see a notification in the notification bar while the scanning is in progress.
Ignoring Cell Towers within a group
Sometimes you may get cell towers appear in a group that you do not want to trigger that group. In this case you can click on the cell tower's checkbox within the list of towers in the group screen to disable/enable it within that group.
If you detect a problematic tower that you want to ignore from all groups you can click on the cell tower id and select "Add to global ignore list". This tower will then be ignored whenever it is detected.
From the Cell Tower Groups screen you can click the menu button and select to view recent towers. Here you will see a chronological list of cell towers that have been seen in the recent past, along with the groups those towers are allocated to. If you see a tower that is not in a group that you think it should be (e.g. you know where at home and it's not listed in your home towers) you may click the entry and select to add to the group. You can also add a tower to the global ignore list from this screen.