my suggestion is to grow some seasoning peppers.
I generally prefer Chinense flavors as the Dominant pepper in my Sauces, so my opinion and selection of low/no heat peppers may be bias
...
but here is a quick list I have compiled for you to start with...
List of Low/No heat Peppers for adding to Sauces:
AJI DULCE (I have tried 3 completely different Aji Dulce, I'm sure there are even more) Find which 1 matches the flavor profile and ideally the color profile as well, with what you are attempting to pair it with. these are usually Chinense type despite the name Aji)
CHUPETINHO/BIQUINHO (while i have not personally tried this 1 yet, i'm told it is of medium-low heat with a great Hab/Chinense flavor)
CRIOLLA DE COCINA (Blocky. *mild Annuum from Nicuragua)
DATIL SWEET (red, and Sweet. not yellow like the typical Datil, but offers much of the same Chinense taste w/ a subtle hint of smokiness)
DULCE SOL ( this Yellow/Gold Chinense actually has a bit of heat, but i would still consider it Mild)
GRENADA SEASONING (this 1 smells fantastic when cooking with it, unfortunately a lot of that aromatic flavor is lost while cooking it, it still adds a nice yellow color and some chinense flavor w/o any heat)
HONDURAS WILD (have not yet tried this, it's supposed to be a Mild red seasoning Annuum)
MAYO PIMENTO (have not yet had the opportunity to try this 1 yet either, supposed to be a Mild Red Chinense Pepper)
PUERTO RICAN NO BURN (another that I have yet to aquire, suppose to be a sweet/mild Red Chinense seasoning pepper with pods that start upright and becomes pendant)
ST.LUCIA SEASONING *comes in both red and yellow (another i have yet to try that is supposed to be a Mild seasoning Chinense)
TOBAGO SEASONING (a fantastic Red Mild Chinense that i have seeds for, yet forgot to grow this year
, excellent for supplementing hot red sauces without distracting from the chinense taste)
TRINIDAD PERFUME (my personal favorite yellow no heat Chinense pepper, excellent fragrance when cooking, nice Trinidad chinense taste and bright yellow color that both hold up pretty well to cooking)
TRINIDAD SEASONING (my favorite Red no heat/very mild Chinense pepper, great flavor and red color to add that classic Trinidad Chinense flavor w/o the heat)
TRINIDAD SMOOTH (another mild Trinidad Chinense that I have yet to try)
ZAVORY (a quite common Red no heat Habanero, my opinion is there are others with more flavor fitting these characteristics)
I'm sure there are several that I have forgot at this time, I'll edit them in if I remember them.
I hope this helps, even a little.