Hello Dave,
It's more like me not explaining things clearly. The query relates more to the Bisect command as this is where I usually go to when in Mirror given I work predominantly with walls and am often doing multiple Bisect mirror or mirror and copy whilst still in Bisect. The Mirror/Bisect command currently only works with entities that Bisect is able to select (walls and lines). If other entities are present that are one of the points to bisect then it doesn't work and gives the response "The point entered is too far from an entity".
The wishlist would add the option to left mouse pick or object snap, when in Bisect, to a point as part of the second selection option asked for, as an alternative to "Click second line",
In the screenshot below, this would allow to;
1. Select the horizontal wall,
2. object snap to the circle centre,
3. the mirror line would then automatically be shown between the the two points and at 90 degrees in the one selection.
In the other example, using Bisect doesn't always give what I expect, especially with a busy floor plan with lots of various wall types and this would be due to the location of the control lines of the walls. The light red lines show the bisect lines of the two walls, which is an extension of where the control lines both intersect. This isn't always the mirror line required between the two walls but instead would be as shown by the green lines (which is more the two closest points along two selected walls). Ideally, the sides of the walls selected should be the bisect lines, irrespective on whether it's a control line or not. It's probably easier I just go back a level to the main Mirror menu and use point to point +90' and get used to working that way instead.