Officially, there is no exact date when this feature will stop working.
Keep in mind that the Unified Interface only accepts supported code, so it is very likely that in the next updates especially in the December update when the web interface becomes obsolete.
Our recommendation is that you focus all efforts on changing your code with the highest possible priority, to avoid any future problems.
Important changes (deprecations) coming in Power Apps, Power Automate, and model-driven apps in Dynamics 365
Regards
Jorge L
Microsoft Support Engineer