Scrabble - Parallel Words joined at one letter
The official rules state:
New words may be formed by:

Adding one or more letters to a word or letters already on the board.

Placing a word at right angles to a word already on the board. The new word must use
one of the letters already on the board or must add a letter to it.

Placing a complete word parallel to a word already played so that adjacent letters also form complete words.


And in the scoring examples, the last example shows a similar case to yours - the word BIT is played underneath PASTE as such:
  P A S T E
B I T

with the player scoring for the words BIT, PI and AT which are formed from the running parallel words. So yes, your example is valid - it is a single word, played parallel to an existing word, such that all adjacent tiles result in forming valid English words.