What should be included in the elements? Problem?Hypotheses?Experimentation and Measurement?or What do I want to achieve, my actions, why, what is the result. Is the result obtained the same as the goal I want to achieve, the reason
I use OneNote. Journal is a broad term and contains different categories of data with different structures and purpose.
So i use multiple notebooks. One for thoughts on past events, like in the pure journal sense. Another for planning. Another for full campaign lifecycle, moving page-campaign through stages in structure, and this page is full of checkboxes.
Another one for problem solving. It has for each one root page with problem description and subpages on hypothesis. Their state i put in title like -confirmed, -not c.
So its pretty versatile and you can make up own structure. Can add images, text, all on one page is very convenient, compared for example with todoist.
I suggest reading a book: "a beginner's guide to scientific method"
Hope it helps, ask if anything 
Tim
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Read "Problem Solving 101" by Ken Watanabe
Best book I read on solving problems in a scientific way, and also a very thin book that you can read in a day.