How does one get around online applications where the salary field is
required, what are some general ideas?
Often, the forms are pretty dumb. You can sometimes put $0 or $1 in the required salary fields.
What are some good ways to negotiate between a HR member asking you
directly for omitted information?
You could say "I'd rather not provide that information" and hope for the best.
"This information is required" - is it, really? Are there any general
situations where it really is required, say, for a government funded
"Required" is an attribute of an employer. If the employer decides that it is "required" (for any reason), then it is.
Can one be declined for not providing salary history?
Yes, one can be declined for not providing any required information.
Remember, outside of legal requirements, the employer makes the rules regarding what information you must provide, and what you can decline to provide.
If an employer says "You must provide your salary history" and you choose not to do so, you can (and often will) be bypassed.
The employer has the job you are seeking, the employer makes the rules for obtaining that job. You can choose not to follow the rules, but most of the time that means you won't get the job.
You as the applicant have the rules for gaining your services. If you make it a condition that you be permitted to omit required fields in an application, then you are choosing to narrow the field of potential employers down. That's your choice to make.