thedata <-  data.frame(group= c(0,0,0,0,0,1,1,1,1,1)
                         ,experiment = c(0,0,1,1,1,0,0,1,1,1)
                         ,time = c(1,2,3,4,5,1,2,3,4,5))

$`1`
group experiment time
0          0    1
0          0    2
0          1    3
1          0    1
1          0    2
1          1    3

$`2`
group experiment time
0          0    1
0          0    2
0          1    3
0          1    4
1          0    1
1          0    2
1          1    3
1          1    4

$`3`
  group experiment time
  0          0    1
  0          0    2
  0          1    3
  0          1    4
  0          1    5
  1          0    1
  1          0    2
  1          1    3
  1          1    4
  1          1    5

library(data.table)
setDT(thedata) # convert to data.table
thedata[, split := cumsum(experiment), by = group] # create a splitting variable

thelist = split(thedata, thedata$split)  # split the data frame into experiments
newlist = list(rbind(thelist[[1]], thelist[[(2)]])) # start to append list elements

for(i in 2:(length(thelist) - 1)){
  # append each new experiment to the old appended data frame in the newlist
  newlist[[i]] = rbind(newlist[[i-1]], thelist[[(i+1)]])
}

newlist
[[1]]
   group experiment time split
1:     0          0    1     0
2:     0          0    2     0
3:     1          0    1     0
4:     1          0    2     0
5:     0          1    3     1
6:     1          1    3     1

[[2]]
   group experiment time split
1:     0          0    1     0
2:     0          0    2     0
3:     1          0    1     0
4:     1          0    2     0
5:     0          1    3     1
6:     1          1    3     1
7:     0          1    4     2
8:     1          1    4     2

[[3]]
    group experiment time split
 1:     0          0    1     0
 2:     0          0    2     0
 3:     1          0    1     0
 4:     1          0    2     0
 5:     0          1    3     1
 6:     1          1    3     1
 7:     0          1    4     2
 8:     1          1    4     2
 9:     0          1    5     3
10:     1          1    5     3