Hi
there may be another way, but if you use html in the text you can use the html paragraph <p>text</p>
see attached image, I'm using bold font and writing 2 lines to the action log:
Test text [now_time_timestr]
Trigger test executed
edit: will paste the html code here for you to copy, paste and modify
<html><head><meta http-equiv="Content-Type" content="text/html; charset=utf-8"><style>body, p, td {font-family: Arial; font-size: 14pt;}</style></head><body bgcolor="#f0f0f0"><p><b>Test text [now_time_timestr]</b></p> <p><b>Trigger test executed</b> </p></font></body></html>