I've found several different modes for flow charts in games...
Mode 1: standard Information Processing
Rectangle: Do something. 1 step per box.
Diamond: make a decision
Circle: Start, end, and goto circles
This mode is excellent for combat flowcharts, especially when the dice pools are detailed in the rectangles.
Not so good for adventures
Mode 2: decisions only
typically, ovals or rectangles
Each location is a chunk ending in a decision point.
I've seen this used for good effect in Digest Group Productions Cinematic Nugget adventure format. That format shows the overall flow as a chart connected by by arrows, with each box being a chapter of the adventure. Each chapter likewise has a flowchart of it's encounters, and then each encounter has a large bold headline.
It also is how I tend to write adventures, when I bother to write adventures.
Mode 3: actions only
Typically, one action per rectangle, no decision blocks.
This mode has been used in several games, as a shortcut on the standard information processing model. Rather than have separate decision triangles, boxes with rolls or comparisons have multiple outputs, with the line annotated for the value ranges. Steps with no decision simply have a single line out.
This mode works rather well for process charts, especially encounter trees for an adventure, but it's less clear about where decisions occur. It's very similar to decisions only, but in the scenario case, there are often lots of decisions with no long term impact, and so the flowhchart shows only the one line out for many encounters; overcome them, by any means, and go on to the next. I've not seen it used in about 10 years; it was very easy to draw with 1996 word processors, unlike the traditional diamonds, circles, and rectangles.
I've seen combat encounters marked with lines rayonny, dancety, or even embattled, with non-combat using a line simple, in both modes 2 and 3.
I've seen process charts which used different shading for who was doing that step; these were usually after-market free fan clarifications, usually combat process.
All of them work. The question becomes, which can you draw and use most effectively?
The decisions only mode is often too terse for many people; it's a map to a text. It doesn't stand alone, and there is a tendency to overlook planned encounters which don't affect the overall flow. Sometimes with drastic consequences; in one adventure, the flow-map didn't show a particular encounter which provided the hook for an entire branch of the adventure; the branch point is several encounters later, and was on the chart.
The boxes-only version is easily doable in most current word processors; it was even doable in old-times with formatted monospaced text. It's simple to draw, and readily followed. It can be cluttered, however.