If all the blocks that caused the error still exists, probably the constant is hidden somewhere. In block parameters window many parameters are just hidden and they keep their last state. If you used a constant in a block and then decided to use another parameter, the constant will still remain.
Everything that can make work easier is a great idea of course. Well, at the moment you can copy/paste blocks, but constants and variables can be only copied by download/reupload the same project.
By the way I found a little bug in the last local builds when uploading project that was previously downloaded - the list of projects dows not grow. If that happens to someone, find a file named "list.ini" somewhere in 'Data/" and delete it.
This will not work because this include file does not exists on the server (web version uses compilator that is on the server). It should work on the local version because it uses local compilator, files and folders. I think I can make the web version to work with the local compilator in future (when using the browser plugin of course), but now the only way to export file with something that is missing inside is to export it as .mq4/.mq5 file.
Actually I think that "Once per positions" is not suitable to be used before the general Buy now or Sell now. Once per positions means "When there are X positions, then pass once", but you need to have positions from somewhere.
There is a big difference when you put blocks in this order "Once per.. -> Condition", or like this "Condition -> Once per...". Maybe the arrangement is not correct. Also, "Once per positions" may wants to have positions in order to work. I made it to not pass until the positions count is not enough. Buy the way "Time bomb" blocks are not suitable for backtesting, don't believe any backtest results using these blocks. This is because they work with time, but in backtesting (even with real ticks data) the time is not exactly the same as in the real world.
This is very good 
For the moment I don't use any external files, but who knows...
You can also check C:\Users\XXXX\AppData\Local\VirtualStore. I really recommend turning off UAC
What means that you cannot view the MT5 platform?
When "Once per bar" is placed at top level under "on Tick", it passes once when a new bar is created (at the first tick from the new bar). If it is placed under some condition, then it could pass "anywhere".
Me too. What is the problem? But describe it in a way that I will understand it 
Maybe I can't understand the question
There is a block called "Hours filter" which have less setting, but I think it will be easy to understand it. Backtest these blocks with "Draw arrow" block. In other words - Hours filter -> Draw arrow. If you add Once per bar just after Hours filter, this will give you 1 signal, otherwise the block will pass at every tick in the whole period of time.
Trailing stop has settings like:
Trailing stop - the size (in pips) where to put the SL
Trailing step - how often to make moves. If step is 10 pips, it will move SL in every 10 pips of profit. If it is 0, it will move it in every price that is bigger than SL+TrailingStop.
Trailing start parameter - when to start trailing stop functionality. You can put 10 pips here, and until you have 10 pips in profit, Trailing stop will not work, no matter what are the settings.
For you, I think the settings are:
Stop - 20
Step - 10
Start - 10
This can explain how trailing stop actually works. Here we have the same trailing stop functionality on the left and on the right. Well, without taking care of Start option. http://fxdreema.com/demo/mt4-9975
Can you show me your Time Filter settings?
Actually you can try something - after that block you can place "Draw arrow" block, so you can see at what time and for how long Time Filter block is passing.
Aha, you are talking for "Price relative to". There are other blocks using the same parameter, so I will be ready later.
"Once per positions" block is ready to be tested
All the 3 dynamic modes are in the block now.
Why this is a bug...
What do you want to do with this block in MT5? Because the term "trade" in MT5 is not exactly the same as in MT4.
I like screenshots Maybe this can help: http://fxdreema.com/shared/HfEyg0DVc