with a broadlink you create a bunch of switches.
so you get a switch to turn the volume up.
a switch only has 2 options, on or off.
i dont think there is any way (in HA) to create what you want.
with haaska or emulated hue you will be able to turn on volume up
and with a custom skill there is no option to do it without “ask X”
but i think there can be 1 option and that is to create a routine.
with a routine you create the command “alexa turn up the volume” and you let the routine turn on the volume up switch.
There are a few ways to do what you are trying to do.
Use the emulated_hue component in HA and setup switches that in turn make HA calls to interact with the broadlink. I have mine setup with a ‘Volume’ switch that when I say “Alexa turn on/off volume” she will turn the volume up or down by 5 respectively.
Create a custom Alexa skill (intent) that triggers an action in HA. Doing this you can say “Alexa [Do Something]” and have that trigger an action in HA. This takes a bit more setup as your HA instance needs to be accessible over the internet via HTTPS. There are a number of tutorials using letsencrypt and duckdns to do this. If you can get it working, it gives you the most flexibility with Alexa, as you can also build in custom responses to your commands. For example, I have an intent setup where I can say “Alexa Aziz Light!” and she will turn all the lights on, and play back the audio clip from that scene in The 5th Element.
Sign up for HA Cloud, which I think is still free, but won’t be for forever. From what I understand it greatly simplifies the Alexa integration with HA. (I’ve never used it, as I prefer to figure things out for myself, and am not too keen about yet another monthly fee.)
Haaska and the HA cloud/skill are functionally identical, the difference is with Haaska you spend an hour of your time setting up your own skill, with ha cloud that work is already done but you’ll end up paying a monthly fee for it at some point.