Ash is permanent and can only be removed by cleaning of the DPF. Yes there are some organo-metallic additives which enhance combustion and improve DPF function by reducing soot generation and lowering burn-off temps. These are called catalysts, an example would be something similar to ferrocene or MMT. Lubrizol, Afton among others have developed patented catalysts. I believe Mobil Synergy Diesel Efficient has a catalyst additive in the formula.
These additives may be part of a balanced formula which will have other properties like enhanced lubricity, raise cetane, remove deposits, de-emulsify water, protect against corrosion, etc...
There are also phony additives which likely do nothing other then separate you from hard earned cash. These snake oil additives give dubious results and use deceptive or vague advertising, I'd avoid anything claiming to be a "Secret".
My experience comes from using an MMT based additive. It works, and works very well at reducing soot generation. The others I have not tried.
Common Catalyst additives:
FBC - Iron based
https://betterdiesel.com/
Amalgamated TDR-FL - MMT Based
https://www.amalgamatedinc.com/store/tdr-fl
FPC-1 - ?? Iron based (Ferrocene) ?? -
https://www.fpc1.com/