How to modify src_filer without overriding defaults?

PlatformIO Core
1

By default src_filer is set to

src_filter =  
    +<*>
    -<.git/> -<.svn/>
    -<example/> -<examples/>
    -<test/> -<tests/>

I want to exclude two files as -<BLE*>. If I use src_filter = -<BLE*> in my project ini, it completely overrides the defaults (saying no source file in src/).
How can I only declare the things to be excluded in my src_filer?
One option is

src_filter =  
    +<*>
    -<.git/> -<.svn/>
    -<example/> -<examples/>
    -<test/> -<tests/>
    -<BLE*>

but this is hacky, as I can’t quickly comment out the last line to include it.
Also, are project ini configs only modifiable with = ? Can I use += for multi-line definition?

2

Writing ; at the start of the last line won’t work?

A variable assignment always needs to have a =, multi-line values are done by indenting the next line, then it’s counted as further content.

3

Still feels weird that as soon as you add one inclusion or exclusion to src_filter, the default entries would silently get overridden.
Yes, I can comment out that line individually.
Thanks anyway.