The Musa Composer is a fancy Editor, augmented with Markup. It can also be used to make "internet memes": text on top of an image.
The text and background will show in the white box on top. The left half of the menu below controls how you enter the text: using the onscreen keyboard, or using your system keyboard in overlay mode, in transliteration mode, or in the Roman alphabet. You can also paste text directly into the white box.
The right half controls the appearance of the text and background image. You can use a simple color or an image file on your local disk as background, and you control how the text is aligned within that background. You also control the foreground (ink) color of any part of the text, along with the style, size, and font you select.
To generate a "meme" (an image with text), press Save as Image: the rest of the screen will disappear. Use your Print Screen button to take a snapshot of the screen, then crop away the empty space using your favorite image editing software (like Windows Photos or Apple Photos). So far, there doesn't seem to be a better way. You can also copy your work into the clipboard, as plain text, Musa, or HTML. After using one of the green buttons, you can restore your work by clicking the white box.