How can I file an I-131 without a specific travel plan?

Yes, this is done all the time I indicate multiple trips and travels may be needed for business and personal reasons.

USCIS does not need a detailed travel plan in order to process an I-1311 advance parole travel permit. Tell the truth and provide a reasonable plan and they will likely approve it in four to five months.

Yes. You can file the I-131 without a specific travel plan. You could put TBD for the date or just put an estimated date of travel. It does not need to be exact. You will be issued a multiple-entry advance parole for a year. Now that your I-526 is approved, you can certainly move forward with the filing of I-485 for adjustment of status, I-131 for multiple entry advance parole and I-765 for employment authorization.

You do not need a specific travel plan. Once you file an application for adjustment of status on Form I-485, you can file for a combination employment authorization document and advance parole. You do not need a detailed travel plan in order to obtain same.

An immigration attorney can help you prepare the I-485, I-765 and I-131 in the best way possible.

You may put "TBD" (to be determined) in a date section or an anticipated approximate date of future travel and include the attachment explaining that you may need to travel for business/family reasons but do not have specific travel plans at this point. You may include the list of countries you plan to visit (e.g., your home country).

You can put an approximate date on the application.

If you are not from a country subject to an immigrant visa backlog, you can file I-485/I-131/I-765 packet based on an approved I-526. When completing I-131 for advance parole, you can indicate "presently unknown" for your travel dates.