I find using Excel can be really good for level creation. You can set it up in a square grid layout, then manually enter different letters/codes that are user-friendly into each cell. You can use conditional formatting to alter the look of the cell depending on those codes so you see a rough approximation (using shading, Windings symbols etc) and the best part is that you can then have excel build the entire level code that you can sumply copy and paste into a TXT file.
Below is a screenshot from my current level editor. The left hand section is where I type in letter-codes, conditional formatting makes these look something like graphics, and then the right hand section turns everything into a format I want to use in my CSV file (in this case concatenated 4-digit numbers that I 'readline'). It does this via a lookup table that converts my letter codes into number codes that I will use in my game. I can tweak my levels visiually then just copy and paste the right hand section into a TXT file. Job done!