in Corel Draw the text will already be a vector. You type out the text you want. In object manager you will see it showing text. Objects have a outline and fill to them. So have the text selected, then right click on a color in your color palete. That will assign that color to the outline of the text. Left click a color will change the fill of it. As long as the text is showing as text in the object manager it can be edited as text. If you select the text and right click on the selection you can select to convert text to curves. If you do this the text can no longer be edited as text. But now you can do other things with/to it that you couldn't as text.
I don't think CD can save as STL file, but maybe wrong. To do what I think you are wanting you would create your text in CD and give it a fill color (black?) have the text selected and do file - export - to web. This will allow you to save the text as a png file or some other types it will allow. Then you get a window where you can change the dpi and size and then "save as" where you will name this file. Then you can import this file into Designer to use.
A Series machine purchased in 2007
had 30 minutes running time up till 2-13-15
Ring Neck Blues DC Insert (outstanding job keeping machine clean!), HF DC blower
Designer 3.102, Pattern Editor, Pattern Sculptor, STL Importer, Scanning Probe, 2D Vector Drawing Suite, 3D Pattern Modeling Suite, Centerline text, Conforming Vectors, CarveTight Chuck, Decorative Bit set
Universal Laser ILS series laser engraver with dual laser cartridges 135 watts total with 24" x 48" table and Class 4 module