Currently , If we have to create a schedule using report manager, we need to save a copy of the dashboard with the filters applied and then schedule that particular saved copy. Thus, if for a single report i want to create multiple schedules, i have to create a separate dashboard copy and point the schedule to that copy. It will be much better if we can create the schedule directly on the dashboard and add filters specific to that schedule. The only option i see is to overwrite the dashboard filters using the 'Apply custom filters' option. However, this brings up a JAQL script which the end user may not be familiar with.
Thus, to enhance report manager, it will be better to add the below options:
1) Allow user to create a schedule in report manager from the dashboards page, instead of going to the report manager plugin.
2)Add some form of UI when adding custom filters instead of displaying JAQL code, so end user would be able to easily overwrite the filters in the same dashboard by creating multiple schedules instead of multiple dashboards.
Note: It is possible through a third party plugin, but would be better to incorporate this in the existing report manager plugin.