Thank you for your answer.
It's not possible, they are only few thresholds and it also depends on selected protocol. 100% is fine for programming desoldered devices (in adapters).
I want to use the device as a programmer in an automated programming environment.
The device to be programmed will be attached to the pin header connector and programming speed may be affected by the length of the connection between the programmer and the device.
So it would be nice to have a fine-grained control, because 100% -> 50% is a very drastic decrease.
Does the 100% also depend on the chip that is selected?
If so can this (or any other setting) regarding the chip manipulated?