About 6 of these plants are spaced equally apart in one of my daughter's flower beds, but I don't think they're something we planted.
My first thought was that they were pig/burn/horse/fire weeds, but none of those seem to be matches.

Any ideas?

Would you be mad if I suggested that those look a lot like a plant needing ID on another thread...

All images shown remind me of Goldenrod. Goldenrod are notoriously quite stoloniferous, so if that plant inhabited a garden, it would be possible for it to sprout anywhere that its stolons were cut or disturbed.

Q. E. D.

DISCLAIMER: I'm a self-proclaimed unreconstructed woody plants guy, so take anything I claim here with a grain (or quintillion) of NaCl.

I agree it's a Goldenrod. Maybe Solidago gigantea or Solidago canadensis. There difficult to ID as to species. Those are all most likely connected by runners as mentioned above. (stolons)

John, I wouldn't be the slightest bit mad if you suggested it looked like the photos of Goldenrod submitted for ID on an earlier thread in this forum, but I really still don't think it's Goldenrod
I considered that possibility, but differences in the main stem, midrib of the leaves, and shine and serration of the leaves - plus the fact that it doesn't look like any of the Goldenrod species in my area - leave me doubting.
I may dig it up and relocate it until it blooms, because right now those plants are occupying prime garden bed space in my daughter's yard, and I have excess plants of known genus and species which I would love to offload on her!

Definitely dig one - or all - and show us what you find before replanting! The nature of the plant's root systems are often good separators of mimicking species.

I am and always will unabashedly be a woody plants guy trespassing in the world of herbaceous plants. It wouldn't bother me to be off the mark, but willing to learn more about what I'm looking at.

I will try to dig some up soon, especially the ones growing known plants that we want to thrive, like the Liatris at the base of these mystery plants/possible Goldenrod.