Is there any way to enhance the heat without changing the taste in a hot sauce?

There are a few things that might work. I would probably just add more seeds. The majority of the capsaicin where the heat comes from is in the seeds, while the majority of the flavor is in the flesh. You could just add some seeds from a hot pepper like habanero or cayenne or even more jalapeno seeds.

You could also add some chili pepper that has heat but not a lot of flavor. Some examples include cayenne and chile de arbol. Thai bird and african bird chiles are hot and also don't have a ton of flavor in my opinion.

Another option is to try a chili extract. For example, a habenero extract will have some flavor, but a small amount will add an enormous amount of heat. So you may be able to get away with an amount small enough not to add much flavor, while at the same time kicking up your heat to the desired level.

Personally I like habenero, esp in El Yucateco sauce, which I often add straight to hot sauces.

Capsaicin, by itself, is pure heat with no noticeable flavour whatsoever.

You can buy capsaicin extract; it's a little hard to find but it is available. Usually it's somewhat diluted, i.e. the linked one has vegetable oil, but it's still 500,000 SHU (truly pure capsaicin would be 15 million).

A drop of the "pure cap" brand is about 5 times hotter than a habanero. Use that much and you'll probably be in agony. You usually need to take a single drop and dilute it, then use some of the diluted quantity. Although that brand might be diluted enough already to use without further dilution.