I will repeat some advice you will hear often on this site:

Pictures would be helpful.

Symmetry is overrated.

Seriously, though, pictures would be helpful, because I can't visualize what you are saying.

Also perfect symmetry is only noticed when you are looking at something from the exact angle that the symmetry is based on. If being an inch or so (just guessing since I don't have a picture) off of perfect symmetry improves function dramatically, then that is what you should do.

Sometimes the easiest solution is the best solution.

Photos and a floor plan may result in more possible solutions.

Even if there is such a hinge, the cabinet door when open will partially block access to the cabinet interior. Alternatively, you can install a hinge restrictor that will stop the cabinet door from fully opening and hitting the towel rail. Your access to the cabinet area may be more limited depending on the cabinet door’s angle when open to the towel rail.

If you can’t move the towel rail, a better solution to have full cabinet access is to live with the filler piece/asymmetry or for symmetry use filler pieces on both ends or use smaller cabinet widths.

Another alternative. Leave the door off, use the space as open shelves. Get some nice baskets to keep whatever in if you feel the need.

Take the towel rail away and use a hook thta clears the door that heated towel rack is in te wrong place or get over the need for symmetry do what what needs doing Yes pictures are a must always when posting questions. I do not understand this question as to why this is still something you can redesign , do you not have all the cabinets already?

So you take 4 days to answer texts? We ask for pictures and if you want help we need them.