Looking for a website with a good, customizable explore feature, for finding cheap flights in a specific, but flexible time frame

Hi, I am currently looking for a cheap ticket to go anywhere from where I am, inside of a relatively specific, but flexible time frame.

My problem is that on all the websites I checked (including Google Flights and Kayak which are mentioned in the wiki), you only have the option to choose between absolutely precise dates, or super vague timeframes, which both aren't helpful for finding the best flights for my situation.

What I am looking for is simply the same type of exploration feature, but with flexible dates (2nd-23rd of April +/- 3 days for example). I cannot understand how all the big sites I checked didn't have that option.

I tried Kiwi which is the only website I found which actually has this combination of features, but for some reason they don't show me half of the flights I find on Google Flights for example (which is very weird and I have no clue why - it seemed to be way better before).

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Note:
I've already tried asking this in r/Flights, but for some reason my post got automatically removed without an explanation as soon as I posted them. I hope I can get some answers here instead.

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TLDR:

I'm looking for websites with a map that allows you to find the cheapest flights to anywhere during a specific, but flexible timeframe.