I deleted my previous comment, I did not read that the technical solution here was an HDMI splitter. Actually this has nothing to do with Splunk, the question is can your computer using that splitter send 4 video signals. If no, it will not work, otherwise it will and you just need to send 4 browser screens. Depending on your requirements and professional the setup must be, and what is possible for your usecase, I would rather look at virtualization options, or advanced video equipment (hardware on-prem).
@ITWhisperer is correct. You need a dedicated video output for each unique screen being displayed. Depending on the system, you may be able to add a DisplayLink adapter through USB to get the additional screens you are looking for. You will need a compatible operating system as well as enough horsepower on the PC to drive the displays.
Doesn't a HDMI splitter merely replicate the display whereas you stated you wanted different displays on each screen? Essentially, the PC needs to be able to address each screen separately, any splitting/duplication happening outside the PC would be unknown to the PC (I think).