It would seem that if you create a custom trigger
.. and try to use it in the end of a customer journey, using the /Activate a custom trigger/
.. you can only map the attributes to the /Lead ID/
.. the problem is the Lead Id IS NOT stored in the /Lead ID/ column of the Lead table, ...
... its stored in the /Lead/ column of the /Lead/ table
Since you can't map to the /Lead/ column in the /Activate custom trigger/ tile, is would seem impossible to hand over the lead id to a power automate flow (in order to update or delete the lead)