Mom struggles with her walker in the front doorway threshold with main door and screen door

Maybe replace the existing threshold with a shallower threshold (with the corresponding added weather stripping added to the door to prevent water damage). Another option might be to find a hard rubber wedge @ 4" wide on the outside (sort of a mini-ramp) to make it a small slope rather than hard edge. I know they make things like this to place over cables, so maybe cutting one of those lengthwise & somehow secure it butted up against the threshold?

There is a product called a "Automatic door bottom" that can be used to replace the 1/2 'threshold with a flat 1/8" threshold. Also if there is a door closer, replace it with a delayed action closer. Automatic door bottoms are available from Zero International. Make sure to get one with a flexible gasket that stays flexible in cold weather.e

Are you referring to the "speed bump" at the front door.... my Dad is in senior living and he has the same thing where he lives going from his apartment out into the hallway. Since it isn't very high, he can slowly move his rolling walker over the bump.

I don't know if getting that bump lower would help, as then you would need to make the door longer or place a thicker rubber thingee at the bottom of the doors.

A threshold ramp on the interior and exterior would help I think, they can be fairly inexpensive. And maybe a good railing or grab bar too. Sometimes I wish I had automatic doors like they have at the supermarket !

I think I can visualize the situation; my father's front door is similar. It hasn't been a problem - yet - but he also picks up his walker or rollator slightly to step over the threshold when he leaves the house.

I'm not sure there is a good solution; I think it would require, as Windy wrote, someone with carpentry skills, or someone skilled in replacing doors.

One of the concerns I would have is that lowering the threshold could create entry and exit problems, especially since I think (as an amateur) that the gap would allow warm air to escape in winter and cold air to enter. And it might be easier for bugs to get in if there's a gap, unless a piece of flashing were added to the door - that might a solution.

My father years ago built a ramp for his sister to use with her walker to exit the front door, out only to a slab porch. The drop between the door and the porch wasn't significant though, and the slab porch was long enough that the ramp slope was easily to navigate.

I not entirely clear on the issue but it sounds like it may take some major doings to improve the door, sill, step issue. Maybe try a handyman/carpenter.