You can use BricsCAD Direct modeling functionality on your sheet metal bodies.
For example: to cut a slotted hole, all you need is a 2D profile and use the direct editing extrusion feature.
Unnecessary details of the model can be simply deleted.
During Push/Pull operations, the flange thickness is maintained automatically.
The corresponding angle of the existent flange can be changed, also.
If cutouts are not needed anymore, use the window selections in combination with the erase tool to delete them.