my setup
User: SuperUser
Client A = ad_client_id=1000001
Client B = ad_client_id=1000002

Behaviour: SuperUser can't reset default grid - by removing all columns, this issue happens only when SuperUser wants customise window tab in my case in client B after creates grid customisation in client A.

steps to reproduce
1. create client A - customise grid e.g. sales order (idempiere create db. entry to ad_tab_customization to ad_client_id=1000001 as ad_tab_customization_id=1000018)

2. create client B - customise grid sales order again - try to remove all columns (reset grid to default)
Message: doesn't have access
LOG: 12:06:52.922-----------> MTabCustomization.delete: You cannot delete this record, role doesn't have access [138]

summary: without reading the code (evaluate db records), i assume, idempiere try to modify record ad_tab_customization_id=1000018 from client B (ad_client_id=1000002)

suggested solution: save ad_tab_customization to client 0 (superuser client), then improve code MTabCustomization.delete to handle this, OR support ad_tab_customization on client wide. (each client different tab customization)

WDYT ?